In the celebration of the sacraments, that is, in the sacred liturgy, Christ, in the power of the Holy Spirit,signifies and realizes the Paschal mystery of his Passion, Death on the Cross and Resurrection. This mystery does not consist simply in a series of events of the remote past (even if the historicity of those events cannot be overlooked!), but enters the dimension of eternity, because the actor that is, He who acted and suffered in those events was the Word incarnate. Because of this, the Paschal mystery of Christ embraces all times and is being made present in them all (n. 1085) through the sacraments that He himself entrusted to his Church, especially the Eucharistic sacrifice.
Read Uwe Michael Lang’s Column on Liturgical Theology in The Liturgy, Work of the Trinity- Part 2 – The Son (CCC 1084-1090).